The major objective of this proposal is to evaluate any correlation between polymorphic soluble human histocompatibility (HL-A) antigens in the serum and the susceptibility to neoplastic disease. An effort will be made to critically assess the effect of the stage of the disease on the qualitative and quantitative variations of soluble HL-A antigens in the serum of cancer patients. A concerted effort will be made to purify and characterize these antigens by biological and chemical means to gain an understanding of their molecular nature and to correlate chemical structure with biological function. In this regard, the chemical and biological properties of HL-A antigens isolated from the sera of cancer patients and of normal donors will be compared in an attempt to assess to what extent malignant transformation affected these cell surface markers. Additional efforts will be made to evaluate the effect of neoplasia on the immunogenicity of soluble HL-A antigens in the serum of cancer patients. Data from studies outlined in this proposal will be critically evaluated to determine whether any variation of soluble HL-A antigen in the serum of cancer patients can be of prognostic value or useful for the detection of any reoccurrence of neoplasms following therapy. Once this has been established to be the case, microcytotoxic tests and radioimmunoassays will be developed as sensitive immunodiagnostic tools for the early detection of neoplastic disease. It is anticipated that data from the experimental approaches of this proposal will give additional insight into the pathogenesis of some neoplastic diseases and thus hopefully aid in a better understanding of the cancer problem.